sedimentary

Dover Chalk

Calcium Carbonate (CaCO3)

Mohs hardness of 1 to 2, white or light gray color, earthy luster, microcrystalline structure, and uneven fracture.

Identified November 15, 2026More sedimentary →

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Physical properties

Mohs hardness of 1 to 2, white or light gray color, earthy luster, microcrystalline structure, and uneven fracture.

Formed from the accumulation of microscopic calcite shells of marine algae over millions of years during the Cretaceous period.

Used in agriculture for soil neutralization, manufacturing of lime, cement production, and traditional blackboard chalk.

Famous for forming the iconic White Cliffs of Dover along the southeastern coast of England.

Easily identified by its soft, powdery texture and strong fizzing reaction when exposed to dilute hydrochloric acid.

Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion

Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image

Sandstone or Siltstone

Arenite (if sandstone)

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Shale

Fissile Sedimentary Rock

Sandstone

Arenite

Shale

Clastic sedimentary rock